What is an enema?

An enema is a procedure that involves the introduction of a liquid, often a therapeutic solution, into the rectum and colon via the anus. This method is typically used for various medical purposes, including bowel cleansing, administration of medications, or as a means to relieve constipation.

The correct answer identifies an enema as a drug infused into the rectum, which accurately reflects its function and application in medical practice. When drugs are administered this way, they can provide localized treatment to the bowel or be absorbed into the bloodstream more quickly than oral medications, which must pass through the digestive system first.

In contrast, the other options do not accurately describe the nature or function of an enema. For example, the administration of gas through the mouth would involve a different physiological process entirely. Similarly, a solid applied to the skin would indicate topical medication, such as creams or ointments, while a patch used for transdermal delivery refers to a method that allows drugs to be absorbed through the skin over time, neither of which relate to the rectal administration characteristic of an enema.